Some sources may give you information based on NAICS. NAICS is the standard used by federal statistical agencies (and therefore by most others) in classifying business establishments for the purpose of collecting, analyzing, and publishing statistical data related to the U.S. business economy.
Common NAICS Codes for Social Work:
The previous coding system was standard industrial classification (sic) and may still be in many tools.
813319 Social change advocacy organizations
813920 Social workers' associations
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